Operating frequencies of semiconductor devices have increased dramatically as new processing technologies have been developed. At high frequencies, the connections between output drivers and input buffers cannot be treated as an electrical short. Instead, the connections between drivers and buffers need to be characterized as a transmission line having a specific impedance. It is well known for output buffers to have an impedance that matches the impedance of the line which it is driving. Known solutions for matching output buffer impedance to transmission line impedance include allowing for output buffers with programmable impedance that can be fixed. For example, an output buffer may have a programmable impedance in the range of 40 to 70 ohms with a resolution of 5 ohms to match a typical transmission line impedance.
While buffers with programmable impedance are useful for matching specific components to a specific system, such impedance matching techniques do not accommodate variances in transmission line impedance that can occur during high frequency operation. For example, variations in impedance can occur during operation depending upon the specific data pattern been transmitted over one or more data lines because of parasitic capacitance and inductance of the package, as well as because of parasitic capacitance and inductance of the signal traces. An apparatus capable of adjusting the drive strength of output buffers and/or impedance of output buffers to accommodate these dynamic variances in impedance would be useful.